Bastile

Drop-in monkey-patch that replaces HuggingFace Qwen3 ops with optimized CuTile kernels for training on NVIDIA Blackwell GPUs.

Requires: NVIDIA Blackwell (B200 / B100) + CUDA Toolkit 13.1+

Benchmarks

Qwen3-8B (36 layers, 4096 hidden, 32 heads) — single B200, batch_size=1, bf16, AdamW:

Throughput (tokens/sec)

Peak GPU Memory (GB)

Latency (ms/iter)

Bastile's fused linear cross-entropy avoids materializing the full [batch * seq_len, vocab_size] logits tensor, which is the dominant memory cost at longer sequences. This is where the memory savings and throughput gains compound.

Installation

pip install bastile

Prerequisites:

• NVIDIA Blackwell GPU (B200, B100, GB200 or RTX 50 Series Chip)
• CUDA Toolkit 13.1+
• PyTorch 2.9+ with CUDA support

# Inside a CUDA 13.1 container:
pip install bastile

Quick Start

import bastile

# Apply all patches BEFORE loading / creating the model
bastile.apply()

from transformers import Qwen3ForCausalLM

model = Qwen3ForCausalLM.from_pretrained("Qwen/Qwen3-8B")
model.train()

# Train as usual — Bastile automatically uses optimized kernels

Selective patching:

bastile.apply(
    rms_norm=True,                   # CuTile RMSNorm
    swiglu=True,                     # CuTile SwiGLU MLP
    rope=True,                       # CuTile RoPE
    fused_linear_cross_entropy=True,  # CuTile fused linear + CE
)

Reset to original HuggingFace implementations:

bastile.reset()

Kernel Implementations

Bastile patches 4 operations in transformers.models.qwen3.modeling_qwen3. Each has a full forward and backward pass:

Operation	Backend	Source	What it replaces
RMSNorm	CuTile	ops/rms_norm.py	Qwen3RMSNorm
SwiGLU MLP	CuTile	ops/swiglu.py	Qwen3MLP
RoPE	CuTile	ops/rope.py	apply_rotary_pos_emb
Fused Linear Cross-Entropy	CuTile	ops/fused_linear_cross_entropy.py	Qwen3ForCausalLM.forward

RMSNorm — CuTile

Native CuTile RMSNorm with persistent forward and backward kernels. Uses gather/scatter memory access with SM-aware tile sizing.

src/bastile/ops/rms_norm.py → patches Qwen3RMSNorm

SwiGLU MLP — CuTile

Native CuTile kernels using cuda.tile with gather/scatter memory access. Uses flush_to_zero and approximate reciprocal for fast sigmoid on Blackwell. Full backward with recomputation (no extra activation memory).

src/bastile/ops/swiglu.py → patches Qwen3MLP

RoPE — CuTile

CuTile rotary position embedding with compiler-optimized occupancy. In-place rotation on reshaped tensors to minimize memory traffic. Backward reuses the forward kernel by negating sin (inverse rotation identity).

src/bastile/ops/rope.py → patches apply_rotary_pos_emb

Fused Linear Cross-Entropy — CuTile

Replaces the standard lm_head(hidden_states) → logits → cross_entropy(logits, labels) pipeline with a chunked approach. This never materializes the full logits tensor ([batch * seq, 151936] for Qwen3), instead computing cross-entropy in chunks. This is the single biggest memory saver at long sequence lengths.

src/bastile/ops/fused_linear_cross_entropy.py → patches Qwen3ForCausalLM.forward

API Reference

import bastile

bastile.apply()                  # Patch all ops
bastile.apply(rope=False)        # Patch everything except RoPE
bastile.reset()                  # Restore original implementations
bastile.get_patched_ops()        # List currently active patches
bastile.warmup_all_kernels()     # Pre-compile kernels (avoids JIT lag)
bastile.clear_autotune_cache()   # Clear kernel caches

Running Benchmarks

# Qwen3-8B sequence length sweep (parallel on 3 GPUs)
make bench-8b

# Qwen3-8B sweep (sequential, single GPU)
make bench-8b-seq

# Qwen3-8B FSDP multi-GPU benchmark
make bench-fsdp

# Kernel micro-benchmarks
make bench-rmsnorm
make bench-lce

Why CuTile instead of Triton?

Bastile uses NVIDIA's CuTile (cuda.tile) instead of Triton. On Blackwell (sm_100), CuTile generates native PTX through NVIDIA's own compiler toolchain, while Triton's code generation for sm_100 is still maturing. In our benchmarks, Triton-based kernels (Liger) often underperform raw PyTorch on B200, whereas CuTile kernels consistently match or beat it.

License

MIT